CN112570416B

CN112570416B - Method for cracking circuit board at high temperature by microwaves and application thereof

Info

Publication number: CN112570416B
Application number: CN201910923259.6A
Authority: CN
Inventors: 乔金樑; 刘文璐; 张晓红; 蒋海斌; 李秉海; 戚桂村; 宋志海; 高建明; 蔡传伦; 王湘; 赖金梅; 张红彬; 茹越; 韩朋; 姜超; 郭照琰; 张江茹
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2023-05-12
Anticipated expiration: 2039-09-27
Also published as: CN112570416A

Abstract

The invention discloses a method for cracking a circuit board at high temperature by microwaves and application thereof. The method comprises the steps of contacting a circuit board with a porous composite material, applying a microwave field to the circuit board and the porous composite material under vacuum or inert atmosphere, generating an electric arc by the porous composite material under the microwave and rapidly reaching high temperature, and cracking organic compounds of the circuit board to obtain a combustible gas product mainly divided into carbon monoxide and a metal and nonmetal mixed solid product with loose and easily separated structure. The method of the invention utilizes the electric arc generated in the microwaves to rapidly trigger high temperature, thereby rapidly cracking the waste circuit board, the process is efficient, the gas product is combustible gas with high added value, the recovery efficiency of solid metal and nonmetal is high, and the full component recovery and utilization of the waste circuit board can be realized.

Description

Method for cracking circuit board at high temperature by microwaves and application thereof

Technical Field

The invention relates to the technical field of waste resource recovery and reuse, in particular to a method for cracking a circuit board at a high temperature by microwaves and application of the method in the aspect of recovering waste circuit boards.

Background

Printed Circuit Boards (PCBs) are a necessary component for almost all electronic information products, and are widely used in various industrial fields such as electronic components and electric control. As a substrate material in PCB manufacture, the copper-clad plate mainly comprises a substrate, copper foil and an adhesive. The substrate is composed of a polymer synthetic resin and a reinforcing material. The binder is typically a phenolic resin, an epoxy resin, a polyimide resin, a cyanate resin, a polyphenylene ether resin, or the like. The copper-clad plate produced in China as early as 2000 reaches 16.01 ten thousand tons, and the yield of the printed circuit board in China exceeds Japanese in 2006, so that the copper-clad plate becomes the printed circuit board producing country with the largest world yield. So far, about 40% of PCBs worldwide are produced in china, with a consequent tremendous amount of Waste Printed Circuit Boards (WPCBs). The existing WPCB treatment methods such as mechanical treatment and acid dissolution are focused on the recovery of metals in a circuit board, the effective recovery and utilization of nonmetallic components in the circuit board are less involved, and most of the methods form serious threat to environmental safety. Therefore, the invention of a clean and efficient WPCB treatment method is one of the hot problems in the current research.

Microwaves refer to electromagnetic waves with wavelengths between infrared rays and ultra-high frequency (UHF) radio waves, have very strong penetrating power, have wavelengths between 1m and 1mm, and correspond to frequencies of 300 GHz-300 MHz. The magnetron of the microwave generator receives the power to generate microwaves, the microwaves are transmitted to the microwave heater through the waveguide, and the materials to be heated are heated under the action of the microwave field. The heating mode of microwave is greatly different from the common heat transfer mode, the high-frequency electric field periodically changes the external electric field and the direction at the speed of hundreds of millions of seconds, so that polar molecules in the material vibrate along with the electric field at high frequency, and the material rapidly heats under the action of intermolecular friction extrusion, so that the temperature inside and on the surface of the material can be rapidly increased at the same time. There are many patents which disclose techniques for thermal cracking by utilizing the characteristic of microwaves, such as patent CN102585860, patent CN103252226, patent CN106520176, etc., but all use common microwave sensitive materials such as silicon carbide to generate heat in a microwave field and transfer the heat to thermal cracking materials, so as to achieve the purpose of thermal cracking. In addition, CN105199139 also directly cleaves carbon fiber composite materials with a microwave oven, and carbon fibers in the carbon fiber composite materials are very inefficient, although they can generate heat in the microwave field.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method for effectively recycling resources by cracking a circuit board at a high temperature by microwaves. The porous composite material generating the electric arc in the microwave is utilized to generate the electric arc in the microwave, so that high temperature is rapidly generated, and organic compounds in the waste circuit board are cracked. The cracking gas product is combustible gas with high recycling value, and the solid residue is easy to realize the separation of metal and nonmetal components, so that the high-efficiency recycling of metal and glass fiber is realized. The method realizes the clean and efficient recovery of the whole components of the waste circuit board.

The invention aims to provide a method for cracking a circuit board at high temperature by microwaves.

The method for cracking the circuit board at high temperature by microwaves comprises the following steps:

the circuit board is contacted with the porous composite material, a microwave field is applied to the circuit board and the porous composite material under inert atmosphere or vacuum, and the porous composite material generates electric arc under the microwave and rapidly reaches high temperature, so that organic compounds in the circuit board are cracked; the weight ratio of the circuit board to the porous composite material is 1:99-99:1, preferably 1:50-50:1, more preferably 1:30-30:1, and most preferably 1:10-10:1.

The organic compound in the circuit board is cracked at high temperature, so that a large amount of gas products and solid residues can be obtained; the gas is a combustible gas with high heat value; the solid residue comprises a metal component with loose structure and easy separation and a nonmetal component mainly comprising a glass fiber mixture and the like. The substance of the above-mentioned organic compound may include an organic substance, a mixture containing an organic substance, a composite material containing an organic substance, and the like.

The inert atmosphere is an inert gas atmosphere commonly used in the art, such as nitrogen, helium, neon, argon, krypton or xenon, preferably nitrogen.

The contact mode of the circuit board and the porous composite material can adopt various modes as long as the circuit board is in contact with the porous composite material. Preferably: the waste circuit board is placed on the porous composite material, placed in a cavity formed by the porous composite material, or covered on the lower part by the porous composite material; more preferably, the circuit board is crushed and then contacted with the porous composite material.

The microwave power of the microwave field is 1W-100 KW; preferably 200W to 50KW, most preferably 500W to 20KW; in particular, for example, 700W, 900W or 1500W; the microwave time is 0.1-200 min; preferably 0.5 to 150min, most preferably 1 to 100min; the microwaves generate an arc which can reach 700-3000 ℃, preferably 800-2500 ℃, more preferably 800-2000 ℃ rapidly, so that the circuit board is cracked.

The method for cracking the circuit board at high temperature by microwaves comprises the following steps: an inorganic porous skeleton and a carbon material supported on the inorganic porous skeleton. The load refers to that the carbon material is fixed on the surface and/or the structure of the inorganic porous framework through a certain binding force. The surface refers to all interfaces of the porous framework that can be contacted with a gas phase, and "fixed in the structure" refers to being embedded or anchored within the porous framework itself, not within the pores.

The carbon material accounts for 0.001-99% of the total mass of the porous composite material, preferably 0.01-90%, more preferably 0.1-80%;

the inorganic porous skeleton is an inorganic material with a porous structure; the average pore diameter of the inorganic porous skeleton is 0.2 to 1000. Mu.m, preferably 0.2 to 500. Mu.m, more preferably 0.5 to 500. Mu.m, particularly preferably 0.5 to 250. Mu.m, or 0.2 to 250. Mu.m; the porosity is 1% -99.99%; preferably 10% to 99.9%, more preferably 30% to 99%. The pore size of individual pores is derived from the shortest value in the SEM photograph of the intersection distance of the straight line passing through the center of the pore and the pore profile.

The carbon material is at least one of graphene, carbon nanotubes, carbon nanofibers, graphite, carbon black, carbon fibers, carbon dots, carbon nanowires, products obtained by carbonizing a carbonizable organic substance or products obtained by carbonizing a mixture of carbonizable organic substances, preferably at least one of graphene, carbon nanotubes, products obtained by carbonizing a carbonizable organic substance and products obtained by carbonizing a mixture of carbonizable organic substances.

The mixture of carbonizable organic compounds is a mixture of carbonizable organic compounds, inorganic compounds of non-metal and non-metal compounds, and other organic compounds of non-metal compounds.

The carbonization refers to: and (3) treating the organic matters at a certain temperature under the condition of atmosphere, wherein all or most of hydrogen, oxygen, nitrogen, sulfur and the like in the organic matters volatilize, so that a synthetic material with high carbon content is obtained.

The carbonizable organic matter is preferably an organic polymer compound, and the organic polymer compound comprises a synthetic polymer compound and a natural organic polymer compound; the synthetic polymer compound is preferably rubber or plastic; the plastic includes thermosetting plastic and thermoplastic plastic.

The natural organic polymer compound is preferably at least one of starch, viscose, lignin and cellulose.

The synthetic polymer compound is preferably at least one selected from epoxy resin, phenolic resin, furan resin, polystyrene, styrene-divinylbenzene copolymer, polyacrylonitrile, polyaniline, polypyrrole, polythiophene, styrene-butadiene rubber and polyurethane rubber.

The mixture of carbonizable organics is preferably at least one of coal, natural pitch, petroleum pitch, or coal tar pitch.

The inorganic material of the inorganic porous skeleton is one or a combination of more of carbon, silicate, aluminate, borate, phosphate, germanate, titanate, oxide, nitride, carbide, boride, sulfide, silicide and halide; wherein the oxide is preferably at least one of alumina, silica, zirconia, magnesia, ceria and titania; the nitride is preferably at least one of silicon nitride, boron nitride, zirconium nitride, hafnium nitride, and tantalum nitride; the carbide is preferably at least one of silicon carbide, zirconium carbide, hafnium carbide and tantalum carbide; the boride is preferably at least one of zirconium boride, hafnium boride and tantalum boride.

The inorganic material of the inorganic porous skeleton is more preferably at least one of carbon, silicate, alumina, magnesia, zirconia, silicon carbide, boron nitride, and potassium titanate.

The inorganic porous skeleton is preferably at least one of the following specific skeletons: a carbon skeleton obtained after carbonization of the polymer sponge, a porous skeleton formed by inorganic fibers, an inorganic sponge skeleton, a skeleton formed by stacking inorganic particles, a ceramic sponge skeleton obtained after roasting of a ceramic precursor sponge, and a ceramic fiber skeleton obtained after roasting of a ceramic precursor fiber; preferably, the porous skeleton is a skeleton obtained by carbonizing melamine sponge, a skeleton obtained by carbonizing phenolic resin sponge, a porous skeleton of aluminum silicate fiber (such as aluminum silicate rock wool), a porous skeleton of mullite fiber, a porous skeleton of alumina fiber (such as alumina fiber board), a porous skeleton of zirconia fiber, a porous skeleton of magnesia fiber, a porous skeleton of boron nitride fiber, a porous skeleton of boron carbide fiber, a porous skeleton of silicon carbide fiber, a porous skeleton of potassium titanate fiber, and a ceramic fiber skeleton obtained by calcining ceramic precursor fiber.

The porous structure of the inorganic porous skeleton may be derived from the pore structure of the skeleton material itself, for example in the form of a sponge-like structure; the porous structure can also be formed by stacking fiber materials, such as fiber cotton, fiber felt, fiber board and other structural forms; pore structures, such as sand pack structures, may also result from the accumulation of particulate material; but may also come from a combination of the above. Preferably from a pore structure of stacked fibrous material. In particular, the porous skeleton made of the inorganic fibers described above is a porous structure made up of a skeleton in which fibrous materials are stacked, and does not mean that the fibers themselves have a porous structure.

The porous composite material can generate high-temperature electric arcs in microwaves, such as electric arcs which can heat the porous composite material to more than 1000 ℃ in a 900w microwave field, and the porous composite material is resistant to high temperature, and can resist high temperature of 3000 ℃ at most. The porous composite material for generating electric arc in the microwave is a novel and efficient microwave heating material, and can quickly crack the circuit board and realize the effective recovery of the waste circuit board.

The porous composite material according to the present invention is preferably a porous composite material provided in the applicant's chinese patent application CN 201811264425.8. The contents of chinese patent application CN201811264425.8 are incorporated herein by reference in their entirety.

The method for microwave pyrolysis of a circuit board according to the present invention may include the preparation of the porous composite material. Specifically, the preparation method of the porous composite material preferably comprises the following steps:

a. preparing a carbon material for loading or a carbon material precursor solution or dispersion;

b. immersing the inorganic porous skeleton or the precursor of the inorganic porous skeleton into the solution or the dispersion liquid in the step a, so that the pores of the inorganic porous skeleton or the precursor of the inorganic porous skeleton are filled with the solution or the dispersion liquid;

wherein the carbon material and/or the carbon material precursor accounts for 0.001 to 99.999 percent, preferably 0.01 to 99.99 percent, more preferably 0.1 to 99.9 percent of the total mass of the inorganic porous skeleton material or the inorganic porous skeleton material precursor and the carbon material and/or the carbon material precursor;

c. taking out the porous material obtained in the step b, drying, preferably heating and drying, separating out or solidifying the carbon material or the precursor of the carbon material, and loading the carbon material or the precursor of the carbon material on an inorganic porous skeleton or the precursor of the inorganic porous skeleton; the heating and drying temperature is preferably 50-250 ℃, more preferably 60-200 ℃ and most preferably 80-180 ℃;

if the raw materials adopt carbon materials and inorganic porous frameworks, obtaining the porous composite material generating electric arc in the microwaves after the step c; if the raw material adopts at least one of a carbon material precursor or an inorganic porous skeleton precursor, the following step d) is needed to be continued:

d. Heating the porous material obtained in the step c in inert gas atmosphere, converting the precursor of the inorganic porous skeleton into the inorganic porous skeleton, and/or reducing or carbonizing the precursor of the carbon material to obtain the porous composite material generating electric arc in the microwaves; the heating temperature is 400 to 1800 ℃, preferably 600 to 1500 ℃, more preferably 800 to 1200 ℃.

Among them, preferred is:

the inorganic porous skeleton precursor is a porous material which can be converted into an inorganic porous skeleton; at least one of a ceramic precursor, a porous material of a carbonizable organic compound, or a porous material of a mixture of carbonizable organic compounds.

The carbon material precursor is at least one of graphene oxide, modified carbon nanotubes, modified carbon nanofibers, modified graphite, modified carbon black, modified carbon fibers, and carbonizable organics or a mixture of carbonizable organics. Modified carbon nanotubes, modified carbon nanofibers, modified graphite, modified carbon black, modified carbon fibers refer to carbon materials pretreated by, for example, using a dispersant or a surfactant, or grafting hydrophilic groups to improve the dispersibility of these carbon materials in water or an organic solvent to obtain a stable dispersion; all of these pretreatment means are pretreatment means for improving dispersibility in the prior art. The carbon materials subjected to the above pretreatment such as graphene aqueous dispersion, graphene ethanol dispersion, graphene aqueous slurry, graphene oily slurry, graphene oxide aqueous dispersion, graphene oxide ethanol dispersion, graphene oxide N-methylpyrrolidone dispersion, carbon nanotube aqueous dispersion, carboxylated carbon nanotube aqueous dispersion, carbon nanotube ethanol dispersion, carbon nanotube dimethylformamide dispersion, carbon nanotube N-methylpyrrolidone slurry and the like can be obtained by commercially available ones.

The solvent of the carbon material or the precursor solution or dispersion thereof in the step a can be selected from one or a combination of benzene, toluene, xylene, trichlorobenzene, trichloromethane, cyclohexane, ethyl caproate, butyl acetate, carbon disulfide, ketone, acetone, cyclohexanone, tetrahydrofuran, dimethylformamide, water or alcohols;

wherein the alcohol is preferably at least one selected from propanol, n-butanol, isobutanol, ethylene glycol, propylene glycol, 1, 4-butanediol, isopropanol and ethanol;

the carbon material precursor for load in the preparation method of the invention is preferably a precursor which can be dissolved or dispersed in a solvent friendly to human body and environment before being loaded, so that the preparation process is green. The solvent friendly to human body and environment is at least one selected from ethanol, water and a mixture of the ethanol and the water. I.e. the solvent in step a is more preferably a solvent comprising water and/or ethanol; further preferred are water and/or ethanol.

The solution or dispersion in the step a may be sufficient to dissolve or disperse the carbon material and/or the carbon material precursor in the solvent, and the concentration thereof may be generally 0.001 to 1g/mL, preferably 0.002 to 0.8g/mL, and more preferably 0.003 to 0.5g/mL.

More specifically:

In the preparation method of the invention, when the carbon material loaded on the inorganic porous skeleton is graphene, a graphene oxide aqueous solution is preferably used in the step a.

When the carbon material loaded on the inorganic porous skeleton in the preparation method is carbon nano tube, the carbon nano tube dispersion liquid is preferably used in the step a.

When the carbon material precursor for load is thermosetting plastic, a proper curing system is prepared according to a curing formula commonly used in the prior art of the thermosetting plastic in the step a; to the curing system, optionally one or more additives selected from the group consisting of: curing accelerators, dyes, pigments, colorants, antioxidants, stabilizers, plasticizers, lubricants, flow modifiers or adjuvants, flame retardants, drip retardants, antiblocking agents, adhesion promoters, conductive agents, polyvalent metal ions, impact modifiers, mold release aids, nucleating agents, and the like; the dosage of the additive is conventional, or is adjusted according to the actual requirement. When the carbon material precursor for loading is thermosetting plastic, the thermosetting resin serving as the carbon material precursor is cured after heating in the subsequent step c, and is loaded on the inorganic porous skeleton.

When the carbon material precursor for load is thermosetting plastic, the corresponding good solvent in the prior art is selected in the step a to dissolve the thermosetting plastic and the curing system thereof, so as to obtain the carbon material precursor solution for load.

When the carbon material precursor for load is thermoplastic plastics, common additives in the prior art in the plastic processing process, such as antioxidants, auxiliary antioxidants, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, softeners, antiblocking agents, foaming agents, dyes, pigments, waxes, extenders, organic acids, flame retardants, coupling agents and the like, can be added into the solution of the carbon material precursor for load. The dosage of the auxiliary agent is conventional dosage or is adjusted according to the actual condition.

In step b of the preparation method of the present invention, the pores of the inorganic porous skeleton may be filled with the carbon material for supporting or the carbon material precursor solution or dispersion by extrusion several times or not at all.

The porous material obtained in step b may be removed in step c of the preparation method of the present invention, with or without taking measures including, but not limited to, one or both of extrusion and centrifugation, to remove excess carbon material for loading or carbon material precursor solution or dispersion in the porous material obtained in step b.

The heating in steps c and d of the preparation method of the invention can be preferably microwave heating, which has high efficiency and uniform heating, in particular:

the power of the microwaves in the step c is 1W-100 KW, preferably 500W-10 KW, and the microwave time is 2-200 min, preferably 20-200 min.

The microwave power in the step d is changed into 100W-100 KW, preferably 700W-20 KW; the microwave time is 0.5 to 200min, preferably 1 to 100min.

The heating in step d of the process according to the invention is carried out under an inert gas atmosphere, selected from inert gas atmospheres commonly used in the art, preferably nitrogen.

The equipment adopted in the preparation method is common equipment.

As described above, the preparation method of the porous composite material combines the inorganic porous skeleton and the carbon material to prepare the porous composite material with excellent mechanical properties, and can generate electric arcs in a microwave field so as to quickly generate high temperature, for example, the porous composite material can generate electric arcs in a 900w microwave field so as to raise the temperature of the porous composite material to more than 1000 ℃, the porous composite material is resistant to high temperature, the process flow is simple and easy to implement, and the large-scale preparation is easy to realize.

The circuit board of the method of the invention can be various circuit boards produced under the current technical conditions.

The microwave field in the method of the invention can adopt various microwave devices in the prior art, such as household microwave ovens, industrialized microwave devices (such as microwave thermal cracking reactors) and the like.

The device for placing or carrying the circuit board and the porous composite material in the method can select various containers or pipelines which can be penetrated by microwaves and can resist the high temperature of 1200 ℃ in the prior art, such as quartz crucible, quartz reactor, quartz tube, alumina crucible, alumina reactor, alumina tube and the like.

The method for cracking the circuit board at high temperature by microwaves can further comprise the steps of treating solid residues obtained by cracking the circuit board, separating metal and nonmetal components in the solid residues, and respectively recycling the metal and nonmetal components; and/or collecting a gas product obtained by cracking the circuit board. The above-mentioned separation of solid residue and collection of gaseous product can be carried out by various methods and apparatuses of the prior art, for example, gas collection can be carried out by a gas collection device, and then the subsequent reaction and production can be carried out as fuel or as raw material for chemical industry.

The gas collection is a method usual in the art, preferably under an inert atmosphere. For example, if a household microwave oven is used as a microwave field, the gas collection mode is as follows: filling a quartz crucible carrying waste plastics and porous composite materials into a vacuum bag in a glove box protected by nitrogen, sealing, unscrewing the crucible through the vacuum bag after microwave reaction, and pricking the crucible into the vacuum bag by using a needle cylinder for sampling; an industrial microwave oven (such as a microwave thermal cracking reactor and the like) with an air inlet and an air outlet is adopted, and the gas collection mode is as follows: the reaction process is purged by nitrogen, and the gas outlet is sampled and collected by a gas collecting bag.

Another object of the invention is to provide an application of the method for microwave pyrolysis of circuit boards.

The invention relates to an application of a method for cracking a circuit board at high temperature by microwaves, which is applied to the aspect of recycling waste circuit boards.

The method of the invention utilizes the porous composite material generating the electric arc in the microwave to generate the electric arc in the microwave, thereby rapidly generating high temperature, cracking the circuit board, realizing efficient process, recycling, high process efficiency, high added value of product composition and being capable of realizing the full recycling of the waste circuit board.

Detailed Description

The invention is further illustrated by the following examples; the present invention is not limited by these examples.

Experimental data in the examples were measured using the following instrument and assay method:

1. determination of the mass percentage of the carbon material loaded in the porous composite material obtained in the example:

1) Under the condition that inorganic porous framework materials are adopted in the raw materials, the weight of the inorganic porous framework materials is measured firstly, the weight of the obtained porous composite material is measured after the experiment is finished, and the weight difference of the inorganic porous framework materials and the porous composite material is the weight of the loaded carbon material, so that the mass percentage content of the loaded carbon material in the porous composite material is measured;

2) Taking two parts of inorganic porous skeleton precursors with the same weight under the condition that the inorganic porous skeleton precursors are adopted as raw materials, wherein one of the two parts of inorganic porous skeleton precursors is used as an example, and the other part of inorganic porous skeleton precursors is used as a blank sample, and only the step c and the step d of the preparation method are implemented; after the experiment is finished, the weight of the porous composite material obtained in the embodiment is weighed, the final weight of the blank is weighed, and the weight difference of the porous composite material and the blank is the weight of the loaded carbon material, so that the mass percentage of the loaded carbon material in the porous composite material is measured.

2. In an example, the collected gas was chromatographed by: the gas products collected after cracking were analyzed according to ASTM D1945-14 using a refinery gas analyzer (HP Agilent 7890A, configured with 3 channels, including 1 FID and 2 TCDs (thermal conductivity detectors)). Hydrocarbons were analyzed on the FID channel. A TCD using a nitrogen carrier gas was used to determine the hydrogen content because of the small difference in conductance between the hydrogen and helium carrier gases. Another TCD employing helium as carrier gas for CO and CO detection ₂ 、N ₂ And O ₂ . For quantitative analysis, the response factor was determined by calibrating a gas standard using RGA (refinery gas analysis).

3. The average pore size of the inorganic porous skeleton and the porous composite material is determined by: the pore size of a single pore is determined by the shortest value of the distance between the straight line passing through the center of the single pore and the two intersections of the contour of the pore in a Scanning Electron Microscope (SEM) photograph, and then the average pore size is determined by the numerical average of the pore size values of all the pores shown in the SEM photograph. SEM was used as Hitachi S-4800, hitachi, japan, at 200 times magnification.

4. The porosity measurement method comprises the following steps: porosity was determined with reference to GB/T23561.4-2009.

The starting materials for the examples and comparative examples of the present invention were all commercially available.

Preparation of porous composite materials：

Example 1

(1) Weighing 500ml graphene oxide aqueous dispersion (JCGO-95-1-2.6-W, 10mg/ml, nanjing Jicang nanotechnology Co., ltd.) in a beaker;

(2) 2g of a porous skeleton (phenolic foam, average pore diameter 300 μm, porosity 99%, well-known oasis floral foam Co., ltd.) composed of phenolic resin was taken and immersed in a graphene oxide aqueous dispersion to make the solution fully enter the pores of the porous skeleton;

(3) Taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in a 180 ℃ oven for heating for 1 hour, drying and pre-reducing;

(4) And (3) placing the dried porous material into a household microwave oven (700 w, model M1-L213B, mey) for high-fire microwave treatment for 2min, reducing the prereduced graphene oxide into graphene, carbonizing the phenolic resin skeleton into a carbon skeleton (average pore diameter 200 mu M, porosity 99%), and obtaining the porous composite material of the graphene-loaded carbon porous skeleton, wherein the graphene accounts for 10% of the total mass of the porous composite material, and the electric arc is generated in the microwave.

Example 2

(1) Weighing 500ml of carbon nanotube dispersion (XFDMA, 100mg/ml, nanjing Xianfeng nanomaterial technologies Co., ltd.) in a beaker;

(2) 2g of a porous skeleton (phenolic foam, average pore diameter 200 μm, porosity 99%, ordinary oasis floral foam Co., ltd.) composed of phenolic resin was taken and immersed in the carbon nanotube dispersion liquid so that the carbon nanotube dispersion liquid fully entered the pores of the porous skeleton;

(3) Taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in an oven at 80 ℃ for heating for 5 hours, and drying;

(4) And (3) placing the dried porous material into a tube furnace, carbonizing for 1h at 800 ℃ in a nitrogen atmosphere to obtain the porous composite material of the carbon nano tube supported carbon porous skeleton generating electric arc in microwaves (the average pore diameter of the carbon skeleton is 140 mu m, the porosity is 99%), wherein the carbon nano tube accounts for 30% of the total mass of the porous composite material.

Example 3

(2) Soaking 5g of fibrous cotton porous skeleton (average pore diameter 150 μm, porosity 90%, shandong Lu Yang energy-saving materials Co., ltd.) composed of silicate into carbon nanotube dispersion, and extruding for several times to make the dispersion fully enter into pore canal of porous skeleton;

(3) Taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in a baking oven at 150 ℃ for heating for 2 hours, and drying to obtain the porous composite material of the silicate fiber-loaded porous skeleton of the carbon nano tube which generates electric arc in microwaves, wherein the carbon nano tube accounts for 10 percent of the total mass of the porous composite material.

Example 4

(1) 30g of a powdered phenolic resin (2123, santa Clara Sail Co., ltd.) and 3.6g of hexamethylenetetramine curing agent were weighed into a beaker, 500ml of ethanol was poured in, and stirred with a magnetic rotor for 1 hour until dissolved;

(2) 5g of a fibrous cotton-shaped porous skeleton (average pore diameter of 150 mu m, porosity of 90 percent, shandong Lu Yang energy-saving materials Co., ltd.) formed by silicate is taken and soaked in the prepared solution, and the solution is extruded for a plurality of times, so that the solution fully enters pore channels of the porous skeleton;

(3) Taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in a 180 ℃ oven for heating for 2 hours, drying the solution, and solidifying the phenolic resin;

(4) And (3) placing the dried and solidified porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the silicate fiber porous skeleton loaded with phenolic resin carbonized products generating electric arcs in microwaves, wherein the carbon material accounts for 5% of the total mass of the porous composite material.

Example 5

(1) 50g of liquid phenolic resin (2152, jining Baiyi chemical) is weighed into a beaker, 500ml of ethanol is poured into the beaker, and the mixture is stirred for 1 hour by a magnetic rotor until the mixture is dissolved;

(2) 8g of a fibrous porous skeleton (average pore diameter 100 μm, porosity 85%, shandong Lu Yang energy-saving materials Co., ltd.) composed of alumina was taken and immersed in the prepared solution, so that the solution fully entered the pores of the porous skeleton;

(4) And (3) placing the dried and solidified porous material into a tubular furnace, carbonizing for 1h at 900 ℃ in nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the alumina fiber porous skeleton loaded by phenolic resin carbonized products which generate electric arcs in microwaves, wherein the carbon material accounts for 6% of the total mass of the porous composite material.

Example 6

(1) Weighing 30g of water-soluble starch (pharmaceutical grade, shanghai Ala Biochemical technology Co., ltd.) in a beaker, pouring 500ml of deionized water, and stirring with a magnetic rotor for 1 hour until dissolution;

(2) 8g of fibrous felted porous framework (average pore diameter 100 μm, porosity 85%, shandong Lu Yang energy-saving materials Co., ltd.) composed of alumina is taken and soaked into the prepared solution, so that the solution fully enters the pore canal of the porous framework;

(3) Taking out the soaked porous material, placing into a microwave thermal cracking reactor (XOLJ-2000N, manufactured by Nanj first euro instruments limited company), performing microwave treatment with 10KW power for 2min, and drying the porous material;

(4) And (3) placing the dried porous material into a tube furnace, carbonizing at 1200 ℃ for 1h in a nitrogen atmosphere, and carbonizing water-soluble starch to obtain the porous composite material of the alumina fiber porous skeleton supported by the starch carbonized product which generates electric arc in microwaves, wherein the carbon material accounts for 0.1% of the total mass of the porous composite material.

Example 7

(1) Weighing 50g of water-soluble starch (pharmaceutical grade, shanghai Ala Biochemical technology Co., ltd.) in a beaker, pouring 500ml of deionized water, and stirring with a magnetic rotor for 1 hour until dissolution;

(2) 8g of a fibrous cotton-shaped porous skeleton (average pore diameter 100 μm, porosity 85%, shandong Lu Yang energy-saving materials Co., ltd.) composed of alumina is taken and soaked in the prepared solution, and the solution is extruded for a plurality of times, so that the solution fully enters the pore canal of the porous skeleton;

(3) Taking out the soaked porous material, putting the porous material into a microwave thermal cracking reactor, performing microwave treatment for 2 hours at the power of 500W, and drying the porous material;

(4) And (3) placing the dried porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in nitrogen atmosphere, and carbonizing starch to obtain the porous composite material of the alumina fiber porous skeleton supported by the starch carbonized product which generates electric arc in microwaves, wherein the carbon material accounts for 0.2% of the total mass of the porous composite material.

Example 8

(1) Weighing 2kg of liquid phenolic resin (2152, jining Baiyi chemical industry) in a beaker, pouring 4L of ethanol, and stirring for 1 hour by using a magnetic rotor until the phenolic resin is dissolved;

(2) 2g of a porous skeleton (phenolic foam, average pore diameter 500 μm, porosity 99%, well-known oasis floral foam Co., ltd.) composed of phenolic resin was taken and immersed in the prepared solution, so that the solution fully entered the pores of the porous skeleton;

(3) Taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in a baking oven at 150 ℃ for heating for 2 hours, and drying;

(4) And (3) placing the dried porous material into a microwave thermal cracking reactor (XOLJ-2000N, manufactured by Nanj first Europe instruments Co., ltd.) and carrying out microwave treatment for 100min under the power of 20KW nitrogen atmosphere to obtain the porous composite material of the phenolic resin carbonized product loaded carbon porous skeleton (the average pore diameter of the carbon skeleton is 350 mu m, the porosity is 99%) generating electric arc in the microwave, wherein the carbon material loaded on the inorganic carbon skeleton accounts for 80% of the total mass of the porous composite material.

Example 9

(2) 8g of a fibrous porous skeleton (average pore diameter 100 μm, porosity 80%, jinan dragon thermal ceramics Co., ltd.) composed of magnesium oxide was taken and immersed in the prepared solution, so that the solution fully entered the pores of the porous skeleton;

(4) And (3) placing the dried and solidified porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in nitrogen atmosphere, and carbonizing phenolic resin to obtain a porous composite material of a porous skeleton of the phenolic resin carbonized product loaded magnesium oxide fiber, wherein the carbon material accounts for 3% of the total mass of the porous composite material.

Example 10

(1) Weighing 100g of water-soluble starch (pharmaceutical grade, shanghai Ala Biochemical technology Co., ltd.) in a beaker, pouring 500ml of deionized water, and stirring with a magnetic rotor for 1 hour until dissolution;

(2) 8g of a fibrous porous skeleton (average pore diameter: 150 μm, porosity: 80%) composed of zirconia was taken and immersed in the prepared solution, so that the solution was sufficiently introduced into the pores of the porous skeleton;

(3) Taking out the soaked porous material, placing into a microwave thermal cracking reactor (XOLJ-2000N, manufactured by Nanj first euro instruments limited company), performing microwave treatment for 20min under the power of 3KW, and drying the porous material;

(4) And (3) placing the dried porous material into a tubular furnace, carbonizing for 2 hours at 900 ℃ in nitrogen atmosphere, and carbonizing starch to obtain the porous composite material of the porous skeleton of the zirconium oxide fiber supported by the starch carbonized product which generates electric arc in microwaves, wherein the carbon material accounts for 0.5% of the total mass of the porous composite material.

Example 11

(2) 8g of a fibrous porous skeleton (average pore diameter 100 μm, porosity 80%, jinan dragon thermal ceramics Limited liability company) composed of boron nitride is taken and soaked into the prepared solution, so that the solution fully enters the pore canal of the porous skeleton;

(4) And (3) placing the dried and solidified porous material into a tubular furnace, carbonizing for 1h at 900 ℃ in nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the porous skeleton of the boron nitride fiber supported by the phenolic resin carbonized product which generates electric arc in microwaves, wherein the carbon material accounts for 5% of the total mass of the porous composite material.

Example 12

(1) Weighing 100g of liquid phenolic resin (2152, jining Baiyi chemical industry) in a beaker, pouring 500ml of ethanol, and stirring for 1 hour by using a magnetic rotor until the liquid phenolic resin is dissolved;

(2) 8g of a fibrous porous skeleton (average pore diameter 100 μm, porosity 80%, jinan dragon thermal ceramics Co., ltd.) composed of potassium titanate is taken and soaked in the prepared solution, so that the solution fully enters the pore canal of the porous skeleton;

(4) And (3) placing the dried and solidified porous material into a tubular furnace, carbonizing for 1h at 800 ℃ in nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the potassium titanate fiber porous skeleton supported by phenolic resin carbonized products which generate electric arcs in microwaves, wherein the carbon material accounts for 10% of the total mass of the porous composite material.

Microwave cracking circuit board:

example 13

10g of waste circuit board (the waste circuit board is pre-crushed into small pieces with the area of about 1 cm) ² Irregular small pieces of size, the circuit board was detached from a waste computer motherboard, a brand technical ja), placed in a cavity composed of 50g of a porous composite material generating an arc in the microwaves obtained in example 1, and then the whole was placed in a microwave pyrolysis reactor (MKX-R1C 1B, manufactured by makeshift, singapore, inc.) and after nitrogen protection, treated with a microwave pyrolysis reactor at 900W power for 5 minutes. The porous composite material generates an electric arc in microwaves, thereby rapidly generating high temperature and transmitting the high temperature to the materials to rapidly crack the materials. The gas component obtained by the collection was subjected to gas chromatography. The main components of the pyrolysis gas products are listed in table 1. Solids after completion of the reaction The mass of the residue is 30% before pyrolysis, and the residue comprises a metal component with loose structure and easy separation and a nonmetal component mainly comprising a glass fiber mixture and the like, and the metal and nonmetal part (mainly glass fiber) in the residue can be separated and recovered through simple crushing.

The specific operation of the inside of the cavity formed by the porous composite material for generating the electric arc of the circuit board to be cracked placed in the microwave is as follows: firstly, a part of porous composite materials generating electric arcs in microwaves are placed in a quartz reactor, the porous composite materials are sequentially placed to form a hollow cavity with an upward opening, then, a waste circuit board is placed in the cavity, and finally, the rest porous composite materials are covered on the upper part of the materials.

The same experiment as described above was performed on the samples obtained in examples 2 to 12, and similar experimental phenomena and results were obtained. The mass of the solid residue after the reaction is over is about 28-35% of that before pyrolysis. The porous composites obtained in examples 2-12 all produced an arc in the microwave, thereby rapidly generating high temperatures and delivering them to the material for rapid pyrolysis.

Comparative example 1

10g of the waste circuit board was uniformly mixed with 50g of silicon carbide powder (98.5% by weight, beijing Co., ltd.) and placed in a quartz reaction tank, and then the whole was placed in a microwave reactor (MKX-R1C 1B, manufactured by Qingdao Michaelwis Co., ltd.) and, after nitrogen protection, treated with a microwave thermal cracking reactor at 900W power for 5 minutes. The microwave process does not have any sparks, the waste circuit board is not changed after microwave treatment, and only the bottom of the quartz reaction tank is slightly warmed.

Example 14

Other parameters and steps were the same as in example 13 except for the following:

10g of a waste circuit board was mixed uniformly with 30g of the porous composite material for generating an arc in the microwave obtained in example 6, and then placed in a quartz reaction tank, and then the whole was placed in a microwave pyrolysis reactor (MKX-R1C 1B, manufactured by Tsingtakayama Michaelku Co., ltd.) and, after nitrogen protection, treated with a microwave pyrolysis reactor at 1200W power for 10 minutes. The porous composite material generates an electric arc in microwaves, thereby rapidly generating high temperature and transmitting the high temperature to the materials to rapidly crack the materials. The gas component obtained by the collection was subjected to gas chromatography. The main components of the pyrolysis gas products are listed in table 2. After the reaction is finished, the mass of the solid residue is 32% of that before pyrolysis, the structure between the metal and the substrate is loose, and the metal and nonmetal parts in the solid residue can be separated and recovered through simple crushing.

Example 15

10g of a waste circuit board was mixed uniformly with 15g of the porous composite material for generating an arc in the microwave obtained in example 2, and then placed in a quartz reaction tank, and then the whole was placed in a microwave pyrolysis reactor (MKX-R1C 1B, manufactured by Tsingtakayama Michaelku Co., ltd.) and after nitrogen protection, treated with 900W power for 20 minutes in the microwave pyrolysis reactor. The porous composite material generates an electric arc in microwaves, thereby rapidly generating high temperature and transmitting the high temperature to the materials to rapidly crack the materials. The gas component obtained by the collection was subjected to gas chromatography. The main components of the pyrolysis gas products are listed in table 3. After the reaction is finished, the mass of the solid residue is 30% of that before pyrolysis, the structure between the metal and the substrate is loose, and the metal and nonmetal parts in the solid residue can be separated and recovered through simple crushing.

Example 16

2g of a waste circuit board was taken, uniformly mixed with 60g of the porous composite material for generating an arc in the microwaves obtained in example 10, placed in a quartz reaction tank, and then the whole was placed in a microwave pyrolysis reactor (MKX-R1C 1B, manufactured by Mikewaiter, inc.), and after nitrogen protection, treated with 900W of power for 5 minutes. The porous composite material generates an electric arc in microwaves, thereby rapidly generating high temperature and transmitting the high temperature to the materials to rapidly crack the materials. The gas component obtained by the collection was subjected to gas chromatography. The main components of the pyrolysis gas products are listed in table 4. After the reaction is finished, the mass of the solid residue is 30% of that before pyrolysis, the structure between the metal and the substrate is loose, and the metal and nonmetal parts in the solid residue can be separated and recovered through simple crushing.

Example 17

20g of a waste circuit board was mixed with 5g of the porous composite material for generating an arc in the microwave obtained in example 8, and then placed in a quartz reaction tank, and then the whole was placed in a microwave pyrolysis reactor (MKX-R1C 1B, manufactured by Tsingtakayama Michaelsen Co., ltd.) and after nitrogen protection, treated with a microwave pyrolysis reactor at 1000W for 30 minutes. The porous composite material generates an electric arc in microwaves, thereby rapidly generating high temperature and transmitting the high temperature to the materials to rapidly crack the materials. The gas component obtained by the collection was subjected to gas chromatography. The main components of the pyrolysis gas products are listed in table 5. After the reaction is finished, the mass of the solid residue is 31 percent before pyrolysis, the structure between the metal and the substrate is loose, and the metal and nonmetal parts in the solid residue can be separated and recovered through simple crushing.

TABLE 1

Composition of gaseous product	Volume ratio (vol.%)
		Hydrogen gas	20.36
Carbon monoxide	53.25
		Carbon dioxide	12.72
Methane	3.81
		Ethane (ethane)	0.39
Ethylene	5.02
		Propane	0.14
Propylene	0.90
		Acetylene (acetylene)	1.35
1-butene	0.42
		1, 3-butadiene	0.05
Benzene	0.09
		Others	1.50

TABLE 2

Composition of gaseous product	Volume ratio (vol.%)
		Hydrogen gas	18.00
Carbon monoxide	42.80
		Carbon dioxide	6.90
Methane	14.90
		Ethane (ethane)	2.00
Ethylene	6.00
		Propane	1.00
Propylene	4.70
		Acetylene (acetylene)	1.10
1-butene	0.20
		1, 3-butadiene	0.60
Benzene	0.10
		Others	1.70

TABLE 3 Table 3

Composition of gaseous product	Volume ratio (vol.%)
		Hydrogen gas	15.00
Carbon monoxide	49.60
		Carbon dioxide	9.10
Methane	13.50
		Ethane (ethane)	2.30
Ethylene	4.20
		Propane	0.80
Propylene	2.20
		Acetylene (acetylene)	0.90
1-butene	0.10
		1, 3-butadiene	0.60
Benzene	0.10
		Others	1.60

TABLE 4 Table 4

Composition of gaseous product	Volume ratio (vol.%)
		Hydrogen gas	19.47
Carbon monoxide	48.80
		Carbon dioxide	7.25
Methane	8.80
		Ethane (ethane)	1.0
Ethylene	8.80
		Propane	0.10
Propylene	3.20
		Acetylene (acetylene)	0.80
1-butene	0.30
		1, 3-butadiene	0.07
Benzene	0.08
		Others	1.33

TABLE 5

Composition of gaseous product	Volume ratio (vol.%)
		Hydrogen gas	16.20
Carbon monoxide	47.32
		Carbon dioxide	8.68
Methane	10.1
		Ethane (ethane)	1.80
Ethylene	6.60
		Propane	2.32
Propylene	4.10
		Acetylene (acetylene)	0.80
1-butene	0.08
		1, 3-butadiene	0.10
Benzene	0.20
		Others	1.70

It can also be seen from the data in the table that the cracking products contain a higher proportion of hydrogen and therefore the hydrogen can be collected for use as fuel.

Claims

1. A method for cracking a circuit board by utilizing microwaves at high temperature comprises the steps of contacting the circuit board with a porous composite material, and applying a microwave field to the circuit board and the porous composite material in an inert atmosphere or in vacuum to crack organic compounds in the circuit board; the weight ratio of the circuit board to the porous composite material is 1:99-99:1; the microwave power of the microwave field is 200W-100 KW, and the microwave time is 0.1-200 min;

The porous composite material comprises an inorganic porous skeleton and a carbon material supported on the inorganic porous skeleton, wherein the carbon material accounts for 0.001% -99% of the total mass of the porous composite material;

wherein the carbon material is at least one of graphene, carbon nanotubes, carbon nanofibers, graphite, carbon black, carbon fibers, carbon dots, carbon nanowires, products obtained by carbonization of carbonizable organic substances or products obtained by carbonization of a mixture of carbonizable organic substances; the inorganic material is one or a combination of carbon, silicate, aluminate, borate, phosphate, germanate, titanate, oxide, nitride, carbide, boride, sulfide, silicide and halide;

wherein the inorganic porous skeleton is an inorganic material with a porous structure, the average pore diameter of the inorganic porous skeleton is 0.2-1000 mu m, and the porosity is 1% -99.9%.

2. The method of claim 1, wherein:

the weight ratio of the circuit board to the porous composite material is 1:50-50:1; and/or the number of the groups of groups,

the microwave power of the microwave field is 200W-50 KW; the microwave time is 0.5-150 min.

3. The method of claim 2, wherein:

The weight ratio of the circuit board to the porous composite material is 1:30-30:1; and/or the number of the groups of groups,

the microwave power of the microwave field is 500W-20 KW; the microwave time is 1-100 min.

4. The method of claim 1, wherein:

the carbon material in the porous composite material accounts for 0.01% -90% of the total mass of the porous composite material; and/or the number of the groups of groups,

the average pore diameter of the inorganic porous skeleton is 0.2-500 mu m; the porosity is 10% -99.9%.

5. The method of claim 4, wherein:

the carbon material in the porous composite material accounts for 0.1-80% of the total mass of the porous composite material; and/or the number of the groups of groups,

the average pore diameter of the inorganic porous skeleton is 0.5-500 mu m; the porosity is 30% -99%.

6. The method of claim 5, wherein:

the average pore diameter of the inorganic porous skeleton is 0.5-250 mu m.

7. The method of claim 1, wherein:

the inorganic material is at least one of carbon, silicate, titanate, oxide, carbide, nitride and boride.

8. The method of claim 7, wherein:

the oxide is at least one selected from aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, cerium oxide and titanium oxide; and/or the number of the groups of groups,

The nitride is at least one selected from the group consisting of silicon nitride, boron nitride, zirconium nitride, hafnium nitride and tantalum nitride; and/or the number of the groups of groups,

the carbide is at least one selected from silicon carbide, zirconium carbide, hafnium carbide and tantalum carbide; and/or the number of the groups of groups,

the boride is selected from at least one of zirconium boride, hafnium boride and tantalum boride.

9. The method of claim 1, wherein:

the inorganic porous skeleton is at least one of the following: the ceramic fiber skeleton is obtained by calcining a ceramic precursor sponge, and a ceramic sponge skeleton obtained by calcining a ceramic precursor fiber.

10. The method of claim 9, wherein:

the inorganic porous skeleton is at least one of the following: the ceramic fiber skeleton is obtained by roasting melamine sponge carbonized skeletons, phenolic resin sponge carbonized skeletons, aluminum silicate fiber porous skeletons, mullite fiber porous skeletons, alumina fiber porous skeletons, zirconia fiber porous skeletons, magnesia fiber porous skeletons, boron nitride fiber porous skeletons, boron carbide fiber porous skeletons, silicon carbide fiber porous skeletons, potassium titanate fiber porous skeletons and ceramic precursor fibers.

11. The method of claim 1, wherein:

the carbon material in the porous composite material is at least one of graphene, carbon nanotubes, a product obtained by carbonizing a carbonizable organic compound and a product obtained by carbonizing a mixture of carbonizable organic compounds.

12. The method of claim 11, wherein:

13. The method as recited in claim 12, wherein:

the mixture of carbonizable organic matters is at least one of coal, natural asphalt, petroleum asphalt or coal tar asphalt.

14. The method of claim 11, wherein:

the carbonizable organic compound is an organic polymer compound, and the organic polymer compound comprises a synthetic polymer compound and a natural organic polymer compound.

15. The method as recited in claim 14, wherein:

the synthetic high molecular compound is rubber and/or plastic; the plastic comprises thermosetting plastic and/or thermoplastic plastic;

the natural organic polymer compound is at least one of starch, viscose, lignin and cellulose.

16. The method as recited in claim 14, wherein:

the synthetic high molecular compound is at least one selected from epoxy resin, phenolic resin, oxazine resin, furan resin, polystyrene, styrene-divinylbenzene copolymer, polyacrylonitrile, polyaniline, polypyrrole, polythiophene, styrene-butadiene rubber and polyurethane rubber.

17. The method of claim 1, wherein the porous composite is prepared by a method comprising the steps of:

a. preparing a carbon material for loading and/or a carbon material precursor solution or dispersion;

c. taking out the porous material obtained in the step b, heating, drying, and separating out or solidifying the carbon material or the precursor of the carbon material, and loading the carbon material or the precursor of the carbon material on an inorganic porous skeleton or the precursor of the inorganic porous skeleton;

d. And c, heating the porous material obtained in the step c in an inert gas atmosphere, converting the precursor of the inorganic porous skeleton into the inorganic porous skeleton, and/or reducing or carbonizing the precursor of the carbon material to obtain the porous composite material generating the electric arc in the microwaves.

18. The method of claim 17, wherein:

19. The method of claim 17, wherein:

the carbon material precursor is at least one of graphene oxide, modified carbon nanotubes, modified carbon nanofibers, modified graphite, modified carbon black, modified carbon fibers, and carbonizable organics or a mixture of carbonizable organics.

20. The method of claim 17, wherein:

the solvent of the carbon material or the precursor solution or dispersion liquid in the step a is one or a combination of benzene, toluene, xylene, trichlorobenzene, trichloromethane, cyclohexane, ethyl caproate, butyl acetate, carbon disulfide, ketone, acetone, cyclohexanone, tetrahydrofuran, dimethylformamide, water or alcohols.

21. The method as recited in claim 20, wherein:

the alcohol is at least one selected from propanol, n-butanol, isobutanol, ethylene glycol, propylene glycol, 1, 4-butanediol, isopropanol and ethanol.

22. The method of claim 17, wherein:

the solvent of the carbon material or its precursor solution or dispersion in step a is a solvent comprising water and/or ethanol.

23. The method as recited in claim 22, wherein:

the solvent of the carbon material or the precursor solution or dispersion thereof in the step a is water and/or ethanol.

24. The method of claim 17, wherein:

the concentration of the solution or dispersion liquid in the step a is 0.001-1 g/mL; and/or the number of the groups of groups,

in the step c, heating and drying are adopted, and the heating temperature is 50-250 ℃; and/or the number of the groups of groups,

and d, heating to 400-1800 ℃.

25. The method as recited in claim 24, wherein:

the concentration of the solution or dispersion liquid in the step a is 0.002-0.8 g/mL; and/or the number of the groups of groups,

in the step c, heating and drying are adopted, and the heating temperature is 60-200 ℃; and/or the number of the groups of groups,

and d, heating at 600-1500 ℃.

26. The method as recited in claim 25, wherein:

the concentration of the solution or dispersion liquid in the step a is 0.003g-0.5 g/mL; and/or the number of the groups of groups,

In the step c, heating and drying are adopted, and the heating temperature is 80-180 ℃; and/or the number of the groups of groups,

and d, heating to 800-1200 ℃.

27. The method of claim 17, wherein:

the heating in step c and/or step d is microwave heating.

28. The method of claim 27, wherein:

the power of the microwaves in the step c is 1W-100 KW, and the microwave time is 2-200 min; and/or the number of the groups of groups,

and d, the microwave power of the step is 100W-100 KW, and the microwave time is 0.5-200 min.

29. The method as recited in claim 28, wherein:

the power of the microwaves in the step c is 500-10 KW, and the microwave time is 20-200 min; and/or the number of the groups of groups,

the microwave power in the step d is 700W-20 KW; the microwave time is 1-100 min.

30. The method according to any one of claims 1 to 29, wherein:

processing solid residues obtained by cracking the circuit board, separating metal and nonmetal components in the solid residues, and respectively recycling the solid residues; and/or collecting a gas product obtained by cracking the circuit board.

31. Use of a method for microwave pyrolysis of circuit boards according to one of claims 1 to 30 for recycling waste circuit boards.